A structure of an air conditioning case for assembling a sliding door is described in PTL 1. In PTL 1, the air conditioning case can be divided into a first case section and a second case section by a dividing surface in the vicinity of the door. A guide groove and an insertion opening are provided in the first case section, and a lid member is provided in the second case section. The guide groove supports the door and guides movement of the door. In the first case section, the insertion opening is provided at an end of the guide groove in a door moving direction.
After the door is inserted from the insertion opening of the first case section, the insertion opening can be closed by the lid member by assembling the first and second case sections.
However, due to such a structure that the insertion opening is provided at the end of the guide groove in the first case section and that the insertion opening of the first case section is closed by the lid member of the second case section, the case dividing surface has to be formed in the vicinity of the door. For this reason, a layout of the air conditioning case is restricted, and a flexibility in design of the air conditioning case is low.